A mechanism for the tissue specificity in BAP1 cancer syndrome

Bayesian analysis of the rate of spontaneous malignant mesothelioma among BAP1 mutant mice in the absence of asbestos exposure

Cancers of the mesothelium, such as malignant mesothelioma (MM), historically have been attributed solely to exposure to asbestos. Recent large scale genetic and genomic functional studies now show that approximately 20% of all human mesotheliomas are causally linked to highly penetrant inherited (germline) pathogenic mutations in numerous cancer related genes. The rarity of these mutations in humans makes it difficult to perform statistically conclusive genetic studies to understand their biological effects. This has created a disconnect between functional and epidemiological studies. However, since the molecular pathogenesis of MM in mice accurately recapitulates that of human disease, this disconnect between functional and epidemiological studies can be overcome by using inbred mouse strains that harbor mutation(s) in genes involved in the disease. Most mouse studies have focused on the effect of asbestos exposure, leaving the effects of genetic mutations in the absence of exposure understudied. Here, using existing peer-reviewed studies, we investigate the rate of spontaneous MM among mice with and without germline genetic mutations, in the absence of asbestos exposure. We leveraged these published data to generate a historical control dataset (HCD) to allow us to improve statistical power and account for genetic heterogeneity between studies. Our Bayesian analyses indicate that the odds of spontaneous MM among germline BAP1 mutant mice is substantially larger than that of wildtype mice. These results support the existing biological study findings that mesotheliomas can arise in the presence of pathogenic germline mutations, independently of asbestos exposure.

Biological effects of ubiquitin-specific peptidase 22 on thyroid papillary cancer cells and its mechanism of action

BACKGROUND

In this study, ubiquitin-specific peptidase 22 (USP22) was detected in both thyroid papillary cancer-1 (TPC-1) and normal thyroid epithelial cell lines (HT-ori3), and its biological function was analyzed.

METHOD

Cell culture, resuscitation, and passage, Western blot, and real-time polymerase chain reaction were used.

RESULTS

The expression of USP22 was found to be significantly higher in TPC-1 cancer cells than in normal cells. After silencing of the USP22 gene in TPC-1 cells, the levels of USP22 gene and protein expression were significantly decreased. After 6 h with silencing of the USP22 gene, the migration rate was lower and the cells had become smaller than in the control group (P<0.05). At 24 h, the number of invasive cells was significantly lower than in the control group (P<0.05). A cell viability test showed that the differences between the groups increased on days 4 and 5 (P<0.05). The number of colony-forming cells had also decreased significantly after 10 days (P<0.05) in the USP22-siRNA1 group. Compared with the control group, the protein levels of USP22, cyclin D2, and Bmi-1 were significantly decreased (P<0.05). The decrease of USP22 was positively correlated with the decrease of Bmi-1 and cyclin D2. After silencing of the USP22 gene in normal HT-ori3 cells, the USP22 gene and protein expressions decreased significantly (P<0.05). A cell viability test showed that the difference had increased (P<0.01), and the number of cloned cells had significantly decreased than that in negative group (P<0.01).

CONCLUSIONS

In conclusion, the USP22 gene plays a key role in the growth, proliferation, invasion, and migration of papillary thyroid cancer cells. USP22 possibly exerts its effect in TPC through the Bmi-1 and cyclin D2 pathways. USP22 also plays a crucial role in the growth of normal thyroid cells.